


A Brother Always Knows

by camichats



Series: Imagine James and Sirius Prompts [208]
Category: Harry Potter - J. K. Rowling
Genre: Alternate Universe - No Voldemort, Established Relationship, Fluff, M/M, Misunderstandings, Post-Hogwarts
Language: English
Status: Completed
Published: 2021-03-05
Updated: 2021-03-05
Packaged: 2021-03-18 21:02:14
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,143
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29864019
Author URL: https://archiveofourown.org/users/camichats/pseuds/camichats
Summary: It took Regulus all of two days after reconnecting with his brother to realise that him and Potter were dating, so why the hell didn't Sirius's friends know about the relationship? He asks Sirius, but he's just as confused about it as Regulus is.
Relationships: Regulus Black & Sirius Black, Sirius Black/James Potter
Series: Imagine James and Sirius Prompts [208]
Series URL: https://archiveofourown.org/series/752925
Comments: 4
Kudos: 106





	A Brother Always Knows

**Author's Note:**

> For the prompt: “Hii! I absolutely adore your fics and I love the idea of James and Sirius dating but everyone else being totally oblivious and thinking they’re just really close friends! I was wondering if you could write a story about it if it’s not too much bother ヽ(o♡o)/”

When Regulus and Sirius hadn't been speaking, Regulus had made it a point to not know things about his brother's life. He wasn't part of the family, Regulus didn't miss him, and that meant there was no need to pay attention to Sirius's life. It certainly hadn't hurt that with Sirius over in Gryffindor and Regulus in Slytherin, he would've had to _work_ to know anything about Sirius. As far as House politics were concerned, Regulus shouldn't have wanted to talk to him anyways. 

But then he graduated and left home too, and him and Sirius started talking. It meant that Regulus had a _lot_ to catch up on, and since some of it had been going on for years, Sirius didn't think to mention it. He hit the high points: living with Potter ("You should call him James, Reg.") and working in some muggle garage to bang around on automobiles and motorbikes. Regulus didn't see the point in him working there were there were any number of spellcrafters that would kill to have Sirius working for them, but part of their 'getting along' pact included Regulus not giving him advice. Sirius likewise wasn't allowed to give Regulus advice. 

All of this was to say that Regulus knew he had missed out on a few things, but he'd really thought that Sirius would've told him that him and Potter-- ugh, _James_ \-- were shagging now. It wasn't a surprise, but he still would've liked to have been _told_. 

Regulus had his arms crossed over his chest and was stewing about it while he waited for Sirius to show up. Lily was the only other one there yet, and they were waiting for everyone else outside the restaurant-- muggle, of course. He'd even dressed for the occasion, though that had been both at Sirius's insistence and galleon when he'd taken him shopping. 

"So, Regulus," Lily said. "How've you been?" 

"Fine. And yourself?" 

"Also fine. It's been pretty fine all around, I guess." 

She was making an effort to be nice to her, and Regulus knew that if word got back around to Sirius that Regulus hadn't at least made an attempt to reciprocate, he'd never shut up about it. "Yes. So er, how long have Sirius and- James been dating?" 

"They're not." 

Regulus blinked and looked over at her. "Pardon?" 

"They're not dating." 

"They most certainly are." 

"Did they tell you that?" Lily asked. 

"Well no, but it's obvious." 

"That's just how they act. It's how they've always acted, but they're not together." 

He blinked at her some more. "Is this one of those jokes you people make that I don't understand?" 

"No, I'm not joking. They're really close, so it looks sometimes like they're dating, but they aren't. Trust me on this, Regulus. They're not together." 

He didn't want to insult her, so he just blinked and said, "Any idea when everyone else is supposed to show?" 

* * *

He thought about what Lily had said and her insistence that it was true-- that there was absolutely nothing romantic going on between Sirius and James. Given that Regulus had heard Sirius call him "the absolute love of my life" more than once, he wasn't willing to believe it. 

Also he'd gone over to visit and walked in on them snogging. Several times. Honestly, it's like they couldn't stand to keep their hands to themselves. 

"Sirius?" 

"Yes, dear brother of mine?" Sirius said, because he liked to see all the ways he could annoy Regulus while pretending to be nice. 

"You and James are dating right?" 

Sirius perked up. "You called him James! And yes, we are." 

"Why does your friend Lily think you aren't?" 

He frowned. He was always so expressive. Regulus didn't know how he managed all that emotion; he got tired just thinking about it. "Lily thinks that? Are you sure she wasn't messing with you?" 

"She said she wasn't. She seemed pretty convinced about it, actually." 

"That's weird," Sirius declared. He didn't seem very bothered by it, and why would he be? Lily and his other friends didn't need to _believe_ that they were dating for it to be true. 

"Can I tell her that she's wrong?" 

"Do whatever you want, mate." Then he paused, shooting Regulus a suspicious look. "Within reason." 

Regulus rolled his eyes. Sirius was always so bloody dramatic, and with practically no reason for it. 

* * *

"Did you know that our friends don't know we're dating?" Sirius said as they got changed for bed. 

"How's that possible?" James asked. "We literally live together, in a one bedroom flat." 

"Do they know that it's one bedroom though? They've never been here before." 

"Sure they have." 

"Where was I for that?" Sirius asked. 

"I dunno. Work, probably." James swooped over and gave him a quick kiss before heading to the toilet so he could brush his teeth. "Doesn't really explain why they don't know, though. How'd you find out?" 

"Regulus told me." 

"How did he find it out?" 

"Find out that we were dating? Or find out that apparently, no one else knows?" Sirius asked. 

"The second one," James called, his words slightly muffled from talking around his toothbrush. 

"I dunno. He said that him and Lily were talking, and she said that we weren't dating." 

He spit in the sink then said, "Huh. That's pretty weird. I mean, it's not like we've been hiding it or summat. At _no_ point have we tried to hide it." 

"Right? Like, remember when we first got together, and we talked about it?" 

"Yeah, and we thought that it never would've worked and they would've just gotten pissed with us for not telling them sooner." 

"Sounds about right," Sirius agreed. "Does this mean we have to tell them?" He didn't much like that thought. If they didn't know that him and James were shacking up by now, that was their problem. 

James snorted. "Hell no. It's their own fault they don't know. I bet we make it all the way to our wedding day before they figure it out." 

Sirius considered that for a moment. "I'll take that bet. If Regulus brought it up once, he'll do it again now that he knows he's right." 

"I don't think he cares that much." 

Sirius didn't feel like explaining that while Regulus didn't care, he liked to be right, and that would be plenty to help motivate him. Sirius wouldn't even have to say a word to his brother about the bet; Regulus would go off and do it all on his own. "How bloody long are you going to stay in the washroom?" 

"Why, you afraid that I'm going to find a new not-boyfriend to spend my time with?" James said, snickering. 

"You think you're so funny." 

"I _am_ so funny." 

Yeah, he was, but Sirius wasn't about to tell him that; he knew it anyways. 

**Author's Note:**

> This is from a prompt driven blog @[imaginejamesandsirius](https://imaginejamesandsirius.tumblr.com) on tumblr. Feel free to drop by!


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